Large shallow inlets and bays are complex systems
interlinking the terrestrial and aquatic environments and composed
of an interdependent mosaic of subtidal, intertidal and surrounding
terrestrial habitats. Several of these habitats types are proposed
as Annex I interests in their own right. Large inlets and bays
are large indentations of the coast, generally more sheltered
from wave action than the open coast. They are relatively shallow,
usually averaging less than 30m in depth.

Rias and voes are formed through fluvial erosion,
whereas fjords evolved through glacial action. These significant
differences in development result in various characteristic
natural structures forming within the systems. Fjords tend to
have a shallow seawards rock sill which causes uneven distribution
of salinity throughout the feature. In contrast, rias, with
constant seaward gradients throughout, tend to have evenly mixed
salinity levels. This mixing of water bodies, as with estuarine
systems, is an important characteristic of inlet and bay features.

In many tidal bays and inlets the upper intertidal
area contains areas of mobile mudflats, perhaps with a landward
wetland fringe. This stratification of habitats within the inlet
and bay system can also be seen in the sediments which form
the bed of the system. Generally, the sediments will grade seawards
into silts, sands and even gravels. This differentiation of
sediment bed is an important consideration as different sediment
types may vary in their vulnerability to disturbance.

The description of sedimentology, benthic communities
and disturbance under other feature headings in this section
are also relevant to inlets and bays.

The tables below summarise the potential threats
to inlets and bays from land and waterborne processes.